Method and apparatus for controlling refrigerator cycle
AssigneeKabushiki Kaisha Toshiba
InventorMichika Uesugi
Life of this patent
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Abstract
In case an instantaneous over-current flowing through switching elements is detected between a predetermined rise time point and a predetermined fall time point of each of the PWM control pulses, the output of the duty control circuit is stopped immediately. In other words, the duty factor of the PWM pulse signal to be outputted as it is under the normal conditions is reduced so as to be cut off after the over-current has been detected. Therefore, it is possible to protect the switching elements of the inverter from breakdown due to over-current, without stopping the operation of the compressor and the compressor motor.
Claims6
A method of controlling a refrigeration cycle during which revolution speed of a compressor is controlled by an electronically commutated, brushless DC motor composed of a PWM-controlled inverter and a permanent-magnet AC motor to change a refrigeration capacity thereof, which comprises the steps of:
- detecting instantaneous current value flowing through switching elements of the inverter;
- and
- when the detected instantaneous current value reaches a predetermined level at a point in time between a designated rise time point and a designated fall time point of a PWM control pulse, setting a command value of the PWM control pulse to zero.
A refrigeration cycle control apparatus, having:
- an electronically commutated, brushless DC motor for driving a compressor in a refrigeration cycle, said brushless DC motor being composed of a PWM-controlled inverter and a permanent-magnet AC motor;
- a current detecting circuit for detecting instantaneous value of current flowing through switching elements of said inverter;
- and
- a PWM control circuit for PWM controlling said inverter,
- wherein said PWM control circuit comprises:
- a duty control circuit for outputting each of PWM control pulse signals between a predetermined pulse rise time point and a predetermined pulse fall time point so as to provide a predetermined duty factor to each PWM control pulse signal;
- and
- a duty limit circuit for allowing said duty control circuit to output a zero-level PWM control pulse signal whenever the detected value of said current detecting circuit reaches the predetermined level between the predetermined pulse rise time point and the predetermined pulse fall time point.
A refrigeration cycle control apparatus, comprising:
- an electronically commutated, brushless DC motor for driving a compressor in a refrigeration cycle, said brushless DC motor including a PWM-controlled inverter and a permanent-magnet AC motor;
- a current detecting circuit for detecting an instantaneous value of current flowing through switching elements of said inverter;
- and
- a PWM control circuit for PWM controlling said inverter,
- wherein said PWM control circuit includes
- a duty control circuit for outputting each of PWM control pulse signals between a predetermined pulse rise time point and a predetermined pulse fall time point so as to provide a predetermined duty factor to each PWM control pulse signal, and
- a duty limit circuit for allowing said duty control circuit to output a zero-level PWM control pulse signal whenever the detected value of said current detecting circuit reaches the predetermined level between the predetermined pulse rise time point and the predetermined pulse fall time point, and
- wherein said duty control circuit comprises a counter for outputting the PWM control pulse signals whenever a counter value reaches a count value determined to be corresponding to a pulse period.
Dependencies are inferred from the claim text.